Aquifex pyrophilus is a gram-negative, non-spore forming, rod-shaped bacteria. It is one of a handful of species in the Aquificota phylum, which are a group of thermophilic bacteria that are found near underwater volcanoes or hot springs.
Etymology
Aquifex pyrophilus has a name that references its respiration and its habitat. The name "Aquifex" means "water-maker" in Latin. The name was assigned to A. pyrophilus because it typically uses oxygen as its respiration and water as a byproduct. The name "Pyrophilus" can be broken down into "Pyro" and "Philus". "Pyro" is Latin for fire, heat, or high temperature and "Philus" is a Latin word for "loving". Therefore the term "pyrophilus" can be interpreted as "heat loving" which refers to the habitat A. pyrophilus is typically found in.
Habitat
thumb|[[Kolbeinsey Ridge lies between Greenland, Iceland, and the Jan Mayen Microcontinent. This is the location where Aquifex pyrophilus was discovered. It is a submarine ridge that has high volcanic activity. ]]
The genus Aquifex is a contains some of the most thermophilic bacterium of all known bacteria. A. pyrophilus is an aquatic microbe that is typically found near underwater volcanoes, marine hydrothermal vents, and/or hot springs where temperatures are extremely high and pressure can be immense. A. pyrophilus has shown resistance to ultraviolet light and ionizing radiation. Oxygen is limited near these hydrothermal vents and underwater volcanos because of the extremely high temperature and reducing power of volcanic gases like H<sub>2</sub>S. A. pyrophilus thrives where the oxic and anoxic zones meet in these environments because of the high availability of hydrogen and thiosulfate.
Aquifex pyrophilus was discovered at Kolbeinsey Ridge, North of Iceland by Robert Huber and Karl Stetter in 1992.
Metabolism
thumb|The Aquifex [[electron transport chain when growing in an aerobic environment.]]
A. pyrophilus is strictly chemolithoautotrophic. Due to its small genome, its ability to survive in extreme heat, its ability to be resistant toward ultraviolet light and ionizing radiation, and because of phylogenetic analyses of the small-subunit 16S rRNA gene, A. pyrophilus is thought to be one of the oldest species in the bacteria domain.
Investigations of the phylogenetic position of Aquificales have utilized the concatenated proteins shared within the Aquificales order and A. pyrophilus. Additionally, Aquificales were found to be somewhat closely related to ε-proteobacteria in phylogenetic trees.